Hi, welcome, and sorry to hear of your travails... they are familiar!
First the usual disclaimer, there is no single solution for everybody. We all seem to react a little differently.
I haven't reduced dose on citalopram yet... I was on other meds now and am now trying citalopram. I just went from 10 to 20 and am slowly getting back to more balanced moods. This stuff brings on all manner of anxiety when there's a dose change!
This appears to be true for any dose changes, up or down.
From my readings, it seems that the minimal
time to stabilize at one dose is typically ~2 weeks. By 'stabilize' I mean, get past the primary side effects and so forth. This being the case, it seems likely that you should stay at your current dose through two weeks, then taper down to the next lower dose and stay there for two weeks, etc.
Of course, the correct way to do this is in regular consultation with your doc and therapist, and with a support group in place- family, friends, who I hope can provide encouragement and points of reference regarding your mood changes.
I hope it goes smoothly for you! I think it will, but it does take patience to sort the doses.